Enhancing Upland Rice Performance through Organic Amendments and Nitrogen Fertilizer Application on Ultisols

Abstract

Upland rice cultivation on marginal soils such as Ultisols is gaining attention as a sustainable alternative to lowland rice systems in Indonesia, especially amid rapid land conversion. However, the acidic nature, low nutrient availability, and high aluminum saturation of Ultisols limit crop productivity. This study evaluated the effects of organic amendments and nitrogen fertilization, including their interaction, on agronomic traits and yield of upland rice (Oryza sativa L.). A factorial experiment was conducted using a randomized complete block design from August 2024 to February 2025 in Kedungrandu Village, Patikraja District, Central Java, Indonesia. Treatments included three types of organic amendments (control, rice husk biochar at 8 t ha-1, and composted cattle manure at 16 t ha-1) and five nitrogen rates (0, 50, 100, 150, and 200 kg urea ha-1). Data were analyzed using ANOVA and Duncan's Multiple Range Test at a 5% significance level. Organic amendments and nitrogen fertilization significantly affected plant height, tiller and panicle number, biomass, and grain yield. Their interaction significantly influenced tiller development and 1000-grain weight. These findings highlight the potential of integrating organic and inorganic inputs to improve upland rice performance in nutrient-poor Ultisols.